Positioning System, Lithographic Apparatus and Device Manufacturing Method

ABSTRACT

A positioning system to position a table within a base frame of a lithographic apparatus, the positioning system including first and second actuators and a controller. The first actuator exerting an actuation force on the table. The first actuator being connected to a balance mass constructed and arranged to absorb a reaction force of the first actuator. The controller and second actuator constructed and arranged to exert a compensation force and/or torque to compensate a torque caused by the actuation force exerted by the first actuator on the balance mass.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit under 35 U.S.C. §119(e) to U.S.Provisional Application No. 61/071,126, filed Apr. 14, 2008, which isincorporated by reference herein in its entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to a positioning system, lithographicapparatus and method for manufacturing a device.

2. Background Art

A lithographic apparatus is a machine that applies a desired patternonto a substrate, usually onto a target portion of the substrate. Alithographic apparatus can be used, for example, in the manufacture ofintegrated circuits (ICs). In such a case, a patterning device, which isalternatively referred to as a mask or a reticle, may be used togenerate a circuit pattern be formed on an individual layer of the IC.This pattern can be transferred onto a target portion (e.g., includingpart of, one, or several dies) on a substrate (e.g., a silicon wafer).Transfer of the pattern is typically via imaging onto a layer ofradiation-sensitive material (resist) provided on the substrate. Ingeneral, a single substrate will contain a network of adjacent targetportions that are successively patterned. Conventional lithographicapparatus include so-called steppers, in which each target portion isirradiated by exposing an entire pattern onto the target portion atonce, and so-called scanners, in which each target portion is irradiatedby scanning the pattern through a radiation beam in a given direction(the “scanning”-direction) while synchronously scanning the substrateparallel or anti-parallel to this direction. It is also possible totransfer the pattern from the patterning device to the substrate byimprinting the pattern onto the substrate.

In some systems, there is a positioning system used to position a table,which may be moveable using a planar motor. Reaction forces of theplanar motor in the X, Y and Rz direction are transmitted to a balancemass. The balance mass is moveable over bearings that allow for movementof the balance mass in the X, Y and Rz direction with respect to a baseplate, and does not allow movements, i.e., is stiffly coupled, in the Z,Rx and Ry directions with respect to the base plate. Reaction forces inall degrees of freedom of a fine positioning mechanism are exerted onthe planar motor and transferred to the balance mass. The center of massof the balance mass and the center of mass of an object table are atdifferent positions in the Z-direction, the Z-direction beingperpendicular to the X and Y directions. A consequence of the differencein center of mass is that when the planar motor exerts a horizontalforce in the X and/or Y direction to the object table a torque aroundrespectively the Y and/or X axes is generated in the balance mass.Because the balance mass is stiffly coupled to the base plate in the Rxand Ry directions through the bearings, this torque is transferred tothe base plate. The torque may cause vibrations in the base plate, whichdeteriorates the functioning of the positioning system or a lithographicapparatus in which the positioning system may be used.

SUMMARY

It is desirable to provide a positioning system in which vibrationscaused by a torque transferred from a balance mass to a base plate areminimized.

In an embodiment according to the present invention, there is provided apositioning system, having a first actuator, a controller, and a secondactuator. The positioning system positions a support. The positioningsystem includes a first actuator configured to exert an actuation forceon the support. The first actuator is coupled to a first balance massconstructed and arranged to absorb a reaction force resulting from theactuation force generated by the first actuator. The controller and thesecond actuator are constructed and arranged to exert a compensationforce to compensate a torque caused by the actuation force exerted bythe first actuator on the first balance mass.

In another embodiment of the present invention, there is provided alithographic apparatus including an illumination system, a patterningdevice, a substrate support, a projection system, and a positioningsystem. The illumination system is configured to condition a radiationbeam. The patterning device support is constructed to support apatterning device. The patterning device is capable of imparting theradiation beam with a pattern in its cross-section to form a patternedradiation beam. The substrate support constructed to hold a substrate.The projection system is configured to project the patterned radiationbeam onto a target portion of the substrate. The positioning system isconstructed and arranged to position at least one of the supports. Thepositioning system includes first and second actuators and a controller.The first actuator is configured to exert an actuation force on thesupport. The first actuator is coupled to a first balance massconstructed and arranged to absorb a reaction force resulting from theactuation force generated by the first actuator. The controller and thesecond actuator are constructed and arranged to exert a compensationforce to compensate a torque caused by the actuation force exerted bythe first actuator on the first balance mass.

In a further embodiment of the present invention, there is provided adevice manufacturing method including the following steps. Providing asubstrate that is at least partially covered by a layer ofradiation-sensitive material on a substrate support. Providing apatterning device on a patterning device support. Projecting a patternedbeam of radiation onto the layer of radiation sensitive material.Positioning at least one of the supports. The positioning includesexerting a first force between a first balance mass and the support. Thefirst force moving the support relative to the first balance mass andcontrollably exerting a second force to compensate a torque caused by adifference in position of the center of mass of the first balance massand the support.

Further features and advantages of the invention, as well as thestructure and operation of various embodiments of the invention, aredescribed in detail below with reference to the accompanying drawings.It is noted that the invention is not limited to the specificembodiments described herein. Such embodiments are presented herein forillustrative purposes only. Additional embodiments will be apparent topersons skilled in the relevant art(s) based on the teachings containedherein.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form partof the specification, illustrate the present invention and, togetherwith the description, further serve to explain the principles of theinvention and to enable a person skilled in the relevant art(s) to makeand use the invention.

FIG. 1 depicts a lithographic apparatus according to an embodiment ofthe invention.

FIG. 2 discloses a positioning system including a table which ismoveable with a planar motor wherein the balance mass and the table havea center of mass on a different position.

FIG. 3 discloses a positioning system according to an embodiment of theinvention.

FIG. 4 discloses a positioning system according to an embodiment of theinvention.

FIG. 5 discloses a positioning system according to an embodiment of theinvention.

FIG. 6 discloses a positioning system according to an embodiment of theinvention.

FIG. 7 discloses a positioning system according to an embodiment of theinvention.

The features and advantages of the present invention will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, in which like reference charactersidentify corresponding elements throughout. In the drawings, likereference numbers generally indicate identical, functionally similar,and/or structurally similar elements. The drawing in which an elementfirst appears is indicated by the leftmost digit(s) in the correspondingreference number.

DETAILED DESCRIPTION OF THE INVENTION

This specification discloses one or more embodiments that incorporatethe features of this invention. The disclosed embodiment(s) merelyexemplify the invention. The scope of the invention is not limited tothe disclosed embodiment(s). The invention is defined by the claimsappended hereto.

The embodiment(s) described, and references in the specification to “oneembodiment”, “an embodiment”, “an example embodiment”, etc., indicatethat the embodiment(s) described may include a particular feature,structure, or characteristic, but every embodiment may not necessarilyinclude the particular feature, structure, or characteristic. Moreover,such phrases are not necessarily referring to the same embodiment.Further, when a particular feature, structure, or characteristic isdescribed in connection with an embodiment, it is understood that it iswithin the knowledge of one skilled in the art to effect such feature,structure, or characteristic in connection with other embodimentswhether or not explicitly described.

Embodiments of the invention may be implemented in hardware, firmware,software, or any combination thereof. Embodiments of the invention mayalso be implemented as instructions stored on a machine-readable medium,which may be read and executed by one or more processors. Amachine-readable medium may include any mechanism for storing ortransmitting information in a form readable by a machine (e.g., acomputing device). For example, a machine-readable medium may includeread only memory (ROM); random access memory (RAM); magnetic diskstorage media; optical storage media; flash memory devices; electrical,optical, acoustical or other forms of propagated signals (e.g., carrierwaves, infrared signals, digital signals, etc.), and others. Further,firmware, software, routines, instructions may be described herein asperforming certain actions. However, it should be appreciated that suchdescriptions are merely for convenience and that such actions in factresult from computing devices, processors, controllers, or other devicesexecuting the firmware, software, routines, instructions, etc.

Before describing such embodiments in more detail, however, it isinstructive to present an example environment in which embodiments ofthe present invention may be implemented.

FIG. 1 schematically depicts a lithographic apparatus according to oneembodiment of the invention. The apparatus includes an illuminationsystem (illuminator) IL configured to condition a radiation beam B(e.g., UV radiation or any other suitable radiation), a patterningdevice support or support structure (e.g., a mask table) MT constructedto support a patterning device (e.g., a mask) MA and connected to afirst positioning device PM configured to accurately position thepatterning device in accordance with certain parameters. The apparatusalso includes a substrate table (e.g., a wafer table) WT or “substratesupport” constructed to hold a substrate (e.g., a resist-coated wafer) Wand connected to a second positioning device PW configured to accuratelyposition the substrate in accordance with certain parameters. Theapparatus further includes a projection system (e.g., a refractiveprojection lens system) PS configured to project a pattern imparted tothe radiation beam B by patterning device MA onto a target portion C(e.g., including one or more dies) of the substrate W.

The illumination system may include various types of optical components,such as refractive, reflective, magnetic, electromagnetic, electrostaticor other types of optical components, or any combination thereof, fordirecting, shaping, or controlling radiation.

The patterning device support holds the patterning device in a mannerthat depends on the orientation of the patterning device, the design ofthe lithographic apparatus, and other conditions, such as for examplewhether or not the patterning device is held in a vacuum environment.The patterning device support can use mechanical, vacuum, electrostaticor other clamping techniques to hold the patterning device. Thepatterning device support may be a frame or a table, for example, whichmay be fixed or movable as required. The patterning device support mayensure that the patterning device is at a desired position, for examplewith respect to the projection system. Any use of the terms “reticle” or“mask” herein may be considered synonymous with the more general term“patterning device.”

The term “patterning device” used herein should be broadly interpretedas referring to any device that can be used to impart a radiation beamwith a pattern in its cross-section so as to create a pattern in atarget portion of the substrate. It should be noted that the patternimparted to the radiation beam may not exactly correspond to the desiredpattern in the target portion of the substrate, for example if thepattern includes phase-shifting features or so called assist features.Generally, the pattern imparted to the radiation beam will correspond toa particular functional layer in a device being created in the targetportion, such as an integrated circuit.

The patterning device may be transmissive or reflective. Examples ofpatterning devices include masks, programmable mirror arrays, andprogrammable LCD panels. Masks are well known in lithography, andinclude mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. An exampleof a programmable mirror array employs a matrix arrangement of smallmirrors, each of which can be individually tilted so as to reflect anincoming radiation beam in different directions. The tilted mirrorsimpart a pattern in a radiation beam which is—reflected by the mirrormatrix.

The term “projection system” used herein should be broadly interpretedas encompassing any type of projection system, including refractive,reflective, catadioptric, magnetic, electromagnetic and electrostaticoptical systems, or any combination thereof, as appropriate for theexposure radiation being used, or for other factors such as the use ofan immersion liquid or the use of a vacuum. Any use of the term“projection lens” herein may be considered as synonymous with the moregeneral term “projection system”.

As here depicted, the apparatus is of a transmissive type (e.g.,employing a transmissive mask). Alternatively, the apparatus may be of areflective type (e.g., employing a programmable mirror array of a typeas referred to above, or employing a reflective mask).

The lithographic apparatus may be of a type having two (dual stage) ormore substrate tables or “substrate supports” (and/or two or more masktables or “mask supports”). In such “multiple stage” machines theadditional tables or supports may be used in parallel, or preparatorysteps may be carried out on one or more tables or supports while one ormore other tables or supports are being used for exposure.

The lithographic apparatus may also be of a type wherein at least aportion of the substrate may be covered by a liquid having a relativelyhigh refractive index, e.g., water, so as to fill a space between theprojection system and the substrate. An immersion liquid may also beapplied to other spaces in the lithographic apparatus, for example,between the mask and the projection system. Immersion techniques can beused to increase the numerical aperture of projection systems. The term“immersion” as used herein does not mean that a structure, such as asubstrate, must be submerged in liquid, but rather only means that aliquid is located between the projection system and the substrate duringexposure.

Referring to FIG. 1, the illuminator IL receives a radiation beam from aradiation source SO. The source and the lithographic apparatus may beseparate entities, for example when the source is an excimer laser. Insuch cases, the source is not considered to form part of thelithographic apparatus and the radiation beam is passed from the sourceSO to the illuminator IL with the aid of a beam delivery system BDincluding, for example, suitable directing mirrors and/or a beamexpander. In other cases the source may be an integral part of thelithographic apparatus, for example when the source is a mercury lamp.The source SO and the illuminator IL, together with the beam deliverysystem BD if required, may be referred to as a radiation system.

The illuminator IL may include an adjuster AD configured to adjust theangular intensity distribution of the radiation beam. Generally, atleast the outer and/or inner radial extent (commonly referred to asσ-outer and σ-inner, respectively) of the intensity distribution in apupil plane of the illuminator can be adjusted. In addition, theilluminator IL may include various other components, such as anintegrator IN and a condenser CO. The illuminator may be used tocondition the radiation beam, to have a desired uniformity and intensitydistribution in its cross-section.

The radiation beam B is incident on the patterning device (e.g., mask)MA, which is held on the patterning device support (e.g., mask table)MT, and is patterned by the patterning device. Having traversed thepatterning device (e.g., mask) MA, the radiation beam B passes throughthe projection system PS, which focuses the beam onto a target portion Cof the substrate W. With the aid of the second positioning device PW andposition sensor IF (e.g., an interferometric device, linear encoder orcapacitive sensor), the substrate table WT can be moved accurately,e.g., so as to position different target portions C in the path of theradiation beam B. Similarly, the first positioning device PM and anotherposition sensor (which is not explicitly depicted in FIG. 1) can be usedto accurately position the patterning device (e.g., mask) MA withrespect to the path of the radiation beam B, e.g., after mechanicalretrieval from a mask library, or during a scan. In general, movement ofthe patterning device support (e.g., mask table) MT may be realized withthe aid of a long-stroke module (coarse positioning) and a short-strokemodule (fine positioning), which form part of the first positioningdevice PM. Similarly, movement of the substrate table WT or “substratesupport” may be realized using a long-stroke module and a short-strokemodule, which form part of the second positioner PW. In the case of astepper (as opposed to a scanner) the patterning device support (e.g.,mask table) MT may be connected to a short-stroke actuator only, or maybe fixed. Patterning device (e.g., mask) MA and substrate W may bealigned using mask alignment marks M1, M2 and substrate alignment marksP1, P2. Although the substrate alignment marks as illustrated occupydedicated target portions, they may be located in spaces between targetportions (these are known as scribe-lane alignment marks). Similarly, insituations in which more than one die is provided on the patterningdevice (e.g., mask) MA, the mask alignment marks may be located betweenthe dies.

The depicted apparatus could be used in at least one of the followingmodes:

1. In step mode, the patterning device support (e.g., mask table) MT or“mask support” and the substrate table WT or “substrate support” arekept essentially stationary, while an entire pattern imparted to theradiation beam is projected onto a target portion C at one time (i.e., asingle static exposure). The substrate table WT or “substrate support”is then shifted in the X and/or Y direction so that a different targetportion C can be exposed. In step mode, the maximum size of the exposurefield limits the size of the target portion C imaged in a single staticexposure.

2. In scan mode, the patterning device support (e.g., mask table) MT or“mask support” and the substrate table WT or “substrate support” arescanned synchronously while a pattern imparted to the radiation beam isprojected onto a target portion C (i.e., a single dynamic exposure). Thevelocity and direction of the substrate table WT or “substrate support”relative to the patterning device support (e.g., mask table) MT or “masksupport” may be determined by the (de-)magnification and image reversalcharacteristics of the projection system PS. In scan mode, the maximumsize of the exposure field limits the width (in the non-scanningdirection) of the target portion in a single dynamic exposure, whereasthe length of the scanning motion determines the height (in the scanningdirection) of the target portion.

3. In another mode, the patterning device support (e.g., mask table) MTor “mask support” is kept essentially stationary holding a programmablepatterning device, and the substrate table WT or “substrate support” ismoved or scanned while a pattern imparted to the radiation beam isprojected onto a target portion C. In this mode, generally a pulsedradiation source is employed and the programmable patterning device isupdated as required after each movement of the substrate table WT or“substrate support” or in between successive radiation pulses during ascan. This mode of operation can be readily applied to masklesslithography that utilizes programmable patterning device, such as aprogrammable mirror array of a type as referred to above.

The second positioning system PW, or the first positioning system PM, orboth, includes: a first actuator configured to exert a force on thepatterning device support (e.g., mask table) MT and/or the substratesupport WT, the first actuator being connected to a first balance massconstructed and arranged to absorb reaction forces of the actuator,wherein the first balance mass and the support have a center of mass ofwhich the position is different in a direction perpendicular to amovement direction and the positioning system includes a controller anda second actuator constructed and arranged to compensate a torque causedby the difference in position of the center of mass of the first balancemass and the patterning device support (e.g., mask table MT) and/or thesubstrate support WT.

FIG. 2 discloses a positioning system PW to position a table WT, whichmay be moveable with a planar motor within, for example in a vacuumchamber 3. The planar motor includes stator 2 and translator 35 toposition the table WT in at least the X, Y and Rz direction and ifrequired also in Z, Rx and Ry. Reaction forces of the coarse positioningmechanism (i.e., the planar motor) in the X, Y and Rz direction aretransmitted to a balance mass 6 (e.g., a first balance mass). Thebalance mass 6 is moveable over bearings 5, which allow for movement ofthe balance mass 6 in the X, Y and Rz direction with respect to the baseplate BP, and does not allow movements, i.e., is stiffly coupled, in theZ, Rx and Ry directions with respect to the base plate BP. Reactionforces in all degrees of freedom of the fine positioning mechanism 1 areexerted on the translator 35 and transferred to the balance mass 6. Thecenter of mass of the balance mass 6 and the center of mass of theobject table WT are at different positions in the Z-direction, theZ-direction being perpendicular to the X and Y directions. A consequenceof the difference in center of mass is that when the planar motor exertsa horizontal force in the X and/or Y direction to the object table WT atorque around respectively the Y and/or X axes is generated in thebalance mass 6. Because the balance mass 6 is stiffly coupled to thebase plate BP in the Rx and Ry directions by means of the bearings 5,this torque is transferred to the base plate BP.

FIG. 3 discloses a positioning system PW, according to an embodiment ofthe present invention. The positioning system PW is configured toposition a substrate support (e.g., wafer table) WT, alternatively thepositioning system PW could also be a used to move a patterning devicesupport (e.g., mask table) MT. The substrate support WT is moved by aplanar motor that has a magnet plate that is provided to a balance mass6 and a coil system that is provided to the substrate support WT. Theplanar motor exerts a force F1 on the substrate support WT, which makesthe substrate support WT move in the direction 11 this force alsocreates a reaction force F1 on the balance mass 6.

Since the balance mass 6 has a center of mass 13 which is at a distanceh1 below the center of mass 15 of the wafer table WT, the force F1creates a torque on the base frame BF having a force F2 at a distance h2from the center of mass of the base frame BF of magnitude F1*h1. Tocompensate this torque, a controller CNT is provided that is connectedvia connection 17 to the planar motor so that it is provided with asignal representing the quantity, direction and position of the force F1created by the planar motor.

In one example, the controller includes an input for the quantity ofactuation force exerted by the first actuator and a calculatorconstructed and arranged to calculate a compensation force on the basisof the actuation force. The compensation force calculated by thecalculator and generated by the second actuator generates a torque thatcompensates a torque caused by the difference in position of the centerof mass of the first balance mass and the substrate support WT. The term“compensation force” used herein may encompass the force that isactually generated by the actuator, as well as the torque that resultsfrom the application of the force.

In one example, the controller CNT calculates forces F2 a and F2 b that,via electrical connection 23, can be exerted by the second actuators 21on the balance masses M to compensate for the torque in such a mannerthat the resulting exerted torque on the base frame BF has an equalmagnitude, but an opposite sign, to the disturbance torque withmagnitude h1*F1. To ensure that no net force is exerted in addition tothe compensation torque, F2 a must be equal to F2 b. The controller CNTcalculates the compensation force on the basis of the direction and theposition in which the second actuator can exert the compensation forceso that the torque is compensated. The second actuator 21 moves thesecond balance mass in the first embodiment of the invention in a lineardirection.

In one example, FIG. 3 discloses a positioning system in which torquesare compensated, which are caused by accelerations of the substratesupport WT in the direction 11. Since a planar motor may be used formovements in two directions, the positioning system may also beconstructed and arranged for compensation of the torques in twodirections. A second actuator and a second balance mass, in addition tothe two depicted, may be constructed and arranged to compensate fortorques caused by accelerations of the substrate support WT in adirection substantially perpendicular to the direction depicted by 11.The positioning system may than be provided with three or four secondactuators and balance masses. By moving the second balance massessimultaneously in one direction the positioning system may alsocompensate for forces in the direction of gravity.

FIG. 4 discloses a positioning system according to an embodiment of theinvention. This embodiment is similar to the embodiment of FIG. 3 forthe same reference numbers. According to the embodiment of the inventionshown in FIG. 4, a controller CNT is connected to the second actuator211, which drives a second balance mass M2 in a rotational direction.The actuator rotates the second balance mass M2 so as to create a torqueto compensate for the torque of the base frame BF caused by the forcesF1 exerted by the planar motor on the wafer table WT and the balancemass 6.

FIG. 5 discloses a positioning system according to an embodiment of theinvention. The embodiment of FIG. 5 is similar to the embodiment of FIG.3 for the same reference numbers. According to the embodiment of theinvention shown in FIG. 5, a second actuator 21 exerts a compensationforce in between the balance mass 6 and the second balance mass M. Thecompensation force exerted by the second actuator 21 can be calculatedby the controller CNT. The compensation force equals F1*h1/h2, whereinF1 is the actuation force, h1 is the distance between the centre of massof the substrate support and the centre of mass of the balance mass 6and h2 is the distance between the centre of mass of the balance mass 6and the centre of mass of the second balance mass M.

FIG. 6 discloses a positioning system according to an embodiment of theinvention. This embodiment is similar to the embodiment shown in FIG. 3for the same reference numbers. In the embodiment according to theinvention shown in FIG. 6, a torque resulting from the position mismatchof the center of gravity of the substrate support WT with respect to thebalance mass 6 is compensated with second actuators 212, 214 exertingthe compensation force between the ground floor GF and the base frameBF. The compensation force can be calculated by the formula:

h1*F1=1₁ *F214−1₂ *F212

Wherein 1 ₁, 1 ₂ are the distances between the center of mass of thebalance mass 6 and the second actuators 214, 212 respectively. ForcesF214 and F212 are the compensation forces exerted by the secondactuators 214, 212. To keep the base frame stable at its position thesum of compensation forces F214 and F212 should be zero. The groundfloor GF may have a limited stiffness and therefore the compensationforce may be generated by having a piezo actuator extending its lengthwhereby the ground stiffness should be taken into account.

FIG. 7 discloses a positioning system according to an embodiment of theinvention. This embodiment is similar to the embodiment of FIG. 3 forthe same reference numbers. According to the embodiment shown in FIG. 7,the second balance mass M is suspended from the base frame BF and asecond actuator 21 can exert a compensation force on the second balancemass M to compensate for the torque. The compensation force can becalculated by the controller CNT on the basis of the distance betweenthe centre of gravities h₁ and h₂ and the actuation force F1.

Additionally, or alternatively, according to an embodiment of theinvention, a torque generated by the substrate support WT and itsbalance mass 6 can be compensated for by a counteracting torquegenerated by the patterning device support MT and its balance mass. Thiscompensation can be achieved by placing the balance mass of thepatterning device support MT somewhat above or below the support MTitself, depending on the movement direction of the patterning devicesupport MT with respect to the substrate support WT.

Combinations and/or variations on the above described modes of use orentirely different modes of use may also be employed. For example, it ispossible to combine the torque compensation system of FIGS. 3, 4, 5, 6and 7.

Although specific reference may be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein may haveother applications, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,flat-panel displays, liquid-crystal displays (LCDs), thin-film magneticheads, etc. The skilled artisan will appreciate that, in the context ofsuch alternative applications, any use of the terms “wafer” or “die”herein may be considered as synonymous with the more general terms“substrate” or “target portion”, respectively. The substrate referred toherein may be processed, before or after exposure, in for example atrack (a tool that typically applies a layer of resist to a substrateand develops the exposed resist), a metrology tool and/or an inspectiontool. Where applicable, the disclosure herein may be applied to such andother substrate processing tools. Further, the substrate may beprocessed more than once, for example in order to create a multi-layerIC, so that the term substrate used herein may also refer to a substratethat already contains multiple processed layers.

Although specific reference may have been made above to the use ofembodiments of the invention in the context of optical lithography, itwill be appreciated that the invention may be used in otherapplications, for example imprint lithography, and where the contextallows, is not limited to optical lithography. In imprint lithography atopography in a patterning device defines the pattern created on asubstrate. The topography of the patterning device may be pressed into alayer of resist supplied to the substrate whereupon the resist is curedby applying electromagnetic radiation, heat, pressure or a combinationthereof. The patterning device is moved out of the resist leaving apattern in it after the resist is cured.

The terms “radiation” and “beam” used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.,having a wavelength of or about 365, 248, 193, 157 or 126 nm) andextreme ultra-violet (EUV) radiation (e.g., having a wavelength in therange of 5-20 nm), as well as particle beams, such as ion beams orelectron beams.

The term “lens”, where the context allows, may refer to any one orcombination of various types of optical components, includingrefractive, reflective, magnetic, electromagnetic and electrostaticoptical components.

While specific embodiments of the invention have been described above,it will be appreciated that the invention may be practiced otherwisethan as described. For example, the invention may take the form of acomputer program containing one or more sequences of machine-readableinstructions describing a method as disclosed above, or a data storagemedium (e.g., semiconductor memory, magnetic or optical disk) havingsuch a computer program stored therein.

CONCLUSION

It is to be appreciated that the Detailed Description section, and notthe Summary and Abstract sections, is intended to be used to interpretthe claims. The Summary and Abstract sections may set forth one or morebut not all exemplary embodiments of the present invention ascontemplated by the inventor(s), and thus, are not intended to limit thepresent invention and the appended claims in any way.

The present invention has been described above with the aid offunctional building blocks illustrating the implementation of specifiedfunctions and relationships thereof. The boundaries of these functionalbuilding blocks have been arbitrarily defined herein for the convenienceof the description. Alternate boundaries can be defined so long as thespecified functions and relationships thereof are appropriatelyperformed.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the invention that others can, by applyingknowledge within the skill of the art, readily modify and/or adapt forvarious applications such specific embodiments, without undueexperimentation, without departing from the general concept of thepresent invention. Therefore, such adaptations and modifications areintended to be within the meaning and range of equivalents of thedisclosed embodiments, based on the teaching and guidance presentedherein. It is to be understood that the phraseology or terminologyherein is for the purpose of description and not of limitation, suchthat the terminology or phraseology of the present specification is tobe interpreted by the skilled artisan in light of the teachings andguidance.

The breadth and scope of the present invention should not be limited byany of the above-described exemplary embodiments, but should be definedonly in accordance with the following claims and their equivalents.

1. A positioning system, comprising: a first actuator configured toexert an actuation force on a support, the first actuator being coupledto a balance mass configured to absorb a reaction force resulting fromthe actuation force generated by the first actuator; a controller; and asecond actuator, wherein the controller and the second actuator areconfigured to exert a compensation force to compensate a torque causedby the actuation force exerted by the first actuator on the balancemass.
 2. The positioning system according to claim 1, wherein the torqueconfigured to be compensated by the controller and the second actuatoris caused by a difference in position of a center of mass of the balancemass and the support.
 3. The positioning system according to claim 2,wherein: the center of mass of the balance mass and the support have adifference in position in a first direction; and the first actuator isconfigured to exert the actuation force in a direction perpendicular tothe first direction.
 4. The positioning system according to claim 3,wherein the first direction is substantially parallel a vertical planeor gravity and the direction perpendicular to the first direction issubstantially in a horizontal plane.
 5. The positioning system accordingto claim 1, wherein the first actuator is a planar motor that includes amagnet plate and a coil.
 6. The positioning system according to claim 5,wherein the magnet plate is coupled to the balance mass and the coil iscoupled to the support.
 7. The positioning system according to claim 1,wherein the positioning system includes a base frame configured tomoveably support the table, the balance mass, and the first actuator. 8.The positioning system according to claim 1, wherein the second actuatoris configured to exert the compensation force on another balance mass.9. The positioning system according to claim 8, wherein the secondactuator is configured to exert the compensation force between the baseframe and a surface that supports the base frame.
 10. The positioningsystem according to claim 8, wherein the another balance mass isconfigured to be actuated in a rotational direction by the secondactuator to exert the compensation torque.
 11. The positioning systemaccording to claim 8, wherein: the another balance mass is moveablysuspended from the base frame; and the second actuator is configured toexert the compensation force between the another balance mass and thebase frame.
 12. The positioning system according to claim 7, wherein theanother balance mass is moveably suspended from the first balance mass.13. The positioning system according to claim 1, wherein the controllercomprises: an input configured to receive a signal representative of theactuation force exerted by the first actuator; and a calculatorconfigured to calculate the compensation force based on the actuationforce.
 14. The positioning system according to claim 1, wherein thecontroller is configured to calculate the compensation force based on aposition and direction of the actuation force and a position anddirection of the compensation force.
 15. A lithographic apparatuscomprising: a patterning device support configured to support apatterning device, the patterning device being capable of imparting aradiation beam with a pattern in its cross-section to form a patternedbeam; a substrate support configured to hold a substrate; a projectionsystem configured to project the patterned beam onto a target portion ofthe substrate, and a positioning system configured to position at leastone of the supports, the positioning system including, a first actuatorconfigured to exert an actuation force on the support, the firstactuator being coupled to a balance mass configured to absorb a reactionforce resulting from the actuation force generated by the firstactuator; a controller, and a second actuator, wherein the controllerand the second actuator are configured to exert a compensation force tocompensate for a torque caused by the actuation force exerted by thefirst actuator on the balance mass.
 16. A device manufacturing methodcomprising: supporting a substrate that is at least partially covered bya layer of radiation-sensitive material on a substrate support;supporting a patterning device on a patterning device support;projecting a patterned beam of radiation onto the layer of radiationsensitive material; and positioning at least one of the supports, thepositioning including, exerting a first force between a balance mass andthe support, the first force moving the support relative to the balancemass, and controllably exerting a second force to compensate a torquecaused by a difference in position of a center of mass of the balancemass and the support.
 17. The method according to claim 16, wherein thesecond force is exerted on a another balance mass.